Conventional molding of small parts in large quantity at economic cost has required expensive molds with many cavities, material wasting sprues and complex runners. The present invention is directed to a high speed injector for molding machines to minimize the duration of the molding cycle thereby increasing the number of parts produced per unit of time, and is summarized in the following objects:
First, to provide a molding machine injector intended primarily for use on molding machines having inexpensive molds of small capacity, as for example one to four cavities, for producing parts having relatively thin walls and sufficiently low mass as to undergo rapid cooling to a solid state.
Second, to provide a molding machine injector capable of an extremely fast operation cycle, in the order of one to five seconds, depending mold and injected material characteristics.
Third, to provide a molding machine injector which includes a nozzle having heat transfer retarding means so arranged as to readily maintain the molding material at the most uniform temperature practical, maintaining fluid flow while avoiding excessive heating of the material.
Fourth, to provide a molding machine injector, the nozzle of which is maintained in close proximity to the entrance of the mold utilizing a small accumulation of essentially solidified molding material to effect a seal and a flow control pin within the nozzle is movable to a retracted position, for flow of the molding material into the mold cavity and an extended position closing the mold entrance with it's tip end flush with a surface of the mold cavity to produce a finished part free of any sprue, runner or other excess material.